Title :
Frequency-modulated multimode laser diode for fiber Bragg grating sensors
Author :
Ferreira, L.A. ; Diatzikis, E.V. ; Santos, J.L. ; Farahi, F.
Author_Institution :
INESC, Univ. de Tecnologia Optoelectron. e Electron., Porto, Portugal
fDate :
9/1/1998 12:00:00 AM
Abstract :
A demodulation scheme for fiber Bragg grating (FBG) sensors is presented. It is based on the generation of an electrical carrier by using a modulated multimode laser diode to illuminate the fiber grating. The change in Bragg wavelength is measured by tracking the phase of the carrier at the detector output in either an open- or a closed-loop scheme. A theoretical analysis of the interrogation technique in terms of linearity and dynamic range is presented. Experimental data were obtained for both strain and temperature measurements. Sensitivities of 0.7 με/√Hz and 0.05°C/√Hz were obtained over a dynamic range of ≈60 dB. The application of this demodulation scheme to a multiplexed sensing system is also demonstrated
Keywords :
demodulation; diffraction gratings; fibre optic sensors; laser modes; optical modulation; semiconductor lasers; sensitivity; strain measurement; strain sensors; temperature measurement; Bragg wavelength; closed-loop scheme; demodulation scheme; detector output; dynamic range; electrical carrier; fiber Bragg grating sensors; fiber grating illumination; frequency-modulated multimode laser diode; interrogation technique; modulated multimode laser diode; multiplexed sensing system; open-loop scheme; strain measurements; temperature measurements; theoretical analysis; tracking; Bragg gratings; Demodulation; Diode lasers; Dynamic range; Fiber gratings; Frequency; Optical fiber sensors; Phase detection; Phase measurement; Wavelength measurement;
Journal_Title :
Lightwave Technology, Journal of
